Potential thermal runaway is a critical concern in the charging of valve regulated lead acid storage batteries. Such thermal runaway conditions have lead to fires and explosions due to the reactions of the batteries. This condition is often aggravated by the high ambient temperature conditions in which the battery charging process is forced to operate. The damage due to thermal runaway is often expensive and service depending on the battery power is often disrupted.
This thermal runaway problem has been previously manually controlled with respect to the battery plants located in central offices of telephone systems. Thermal runaway is mainly prevented by continuous manual supervision alert to the occurrence of this thermal runaway possibility in order to enable supervisoyr personal monitoring the battery conditions to take immediate preventative action.
An automatic scheme for preventing thermal runaway is disclosed in Telephony, Oct. 16, 1978, in an article by Jim Plunkett entitled "Battery Monitor Stops Thermal Runaway Cold". In this scheme the battery temperature and charging voltage is monitored by a monitoring device. If either the charging voltage or battery temperature exceeds a preset limit, the application of charging current to the battery is interrupted. This unfortunately terminates the battery charging until conditions improve. It may be desirable to continue charging if it can be performed safely.